Field of the Invention
The present invention relates to an image forming apparatus for forming an image on a sheet.
Description of the Related Art
As a conventional electrophotographic image forming apparatus, the image forming apparatus is widely known that transfers the toner images of respective colors on the intermediate transfer belt in a sequentially superimposed manner and then transfers the toner images borne on the intermediate transfer belt to a recording material in a lump by the transfer roller. Such an image forming apparatus is usually configured such that the transfer roller is able to be separated from the intermediate transfer belt during the jam recovery for facilitating the jam recovery by a user. Specifically, a door rotatable with respect to the main body of the image forming apparatus is provided and the transfer roller is separated from the intermediate transfer belt while being interlocked with an operation of opening and closing of the door.
In view of recording accuracy of an image, it is necessary to set a high contact pressure of the transfer roller to the intermediate transfer belt. In this case, when the pressure is set to 3 kgf to 8 kgf (29.1N to 78.4N) for example, the opening and closing operation of the door becomes heavier in order to generate this contact pressure.
In order to lighten the opening and closing operation of the door, there is a structure in which a transfer unit attached rotatably to the main body of an image forming apparatus and a lock mechanism act in an interlocking manner with the rotation of the door (Japanese Patent Laid-Open No. 2009-251135). In Japanese Patent Laid-Open No. 2009-251135, the position of the secondary transfer roller relative to the body is determined so as to reduce a user operation force when the secondary transfer roller is in contact with the intermediate transfer belt.
In such a conventional image forming apparatus, the user operating force is reduced when opening and closing the door. However, the entire conveying path of the recording material cannot be opened since the transfer unit is provided at the main body of the image forming apparatus so as to be able to rotate. Therefore, when a user has opened the door for recovering jam, the transfer unit may block the conveying path which is disposed in the upstream of the transfer unit from the user's view depending on the location of conveying path for the recording material before entry into the transfer portion, which may deteriorate user's visibility.
Further, a nip of the registration roller for conveying a recording material may not be released, thereby visibility for the conveying path may deteriorate. Furthermore, even though the door can be opened when jam occurs, the recording material remains nipped at the registration roller to which the force of 2 kgf to 4 kgf (19.6N to 39.2N) is applied. Therefore, a user must pull up a recording material more strongly than the nip force of the registration roller when the user handles the recording material, thereby it becomes more difficult to recover jam. On the other hand, when the structure is employed in which the nip of the registration roller is in contact or is separated in accordance with opening and closing of the door, there is a problem that the opening and closing operation becomes heavy due to the contact pressure of 2 kgf to 4 kgf (19.6N to 39.2N).